Armed guards are specially trained in the use of firearms and licensed to carry firearms during their shift. They must be of an even temperament and should have a good understanding of the conditions surrounding the property they are protecting. Armed guards generally make more money than unarmed guards -- for obvious reasons.
Armed guards should only be used in situations requiring protection of money, jewelry, art works, firearms, or other objects which might attract armed robbers. Protect the money which is exposed to the public by making frequent safe-drops, keeping cash register drawers shut whenever possible, and enforcing rigid money-handling procedures. Other valuables should be physically secured, if possible, before exposing them to the public.
It is generally not a good idea for retail establishments to employ armed guards in public areas. If someone is intent on robbing a retail business, there is no way to tell who that person might be, and the guard with the gun becomes the first target. An unarmed guard will deter thieves just as well without becoming a source or cause of violence in the event of a holdup.
An armed guard would be appropriate in a non-public area since access is restricted and any strangers or other unauthorized persons could be quickly turned away, subdued or arrested. Use armed guards judiciously; remember, if someone is injured or killed, you can also be held liable. In many cases, hiring off-duty police officers as armed guards is preferable because it limits the business owner's liability in case someone gets hurt.